Tube bender

ABSTRACT

A tube bending apparatus for simultaneously forming multiple bends in metallic tubing, the tubing being secured at opposite ends and a plurality of double actuating forming or bending heads being used to form the bends, one such double actuating bending head being used for each of the bends.

United States Patent Early [4 May 16,1972

[ TUBE BENDER [72] Inventor: Robert E. Early, Madison Heights, Mich.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[22] Filed: Nov. 23, 1970 [2]] App]. No.: 91,683

52 U.S.Cl ..72/305,72/3l9, 72 399 511 lnt.Cl ..B2ldll/04 581 Field of Search ..,...72 305, 306, 389, 310, 316,

[56] References Cited UNITED STATES PATENTS Green ..72/306 2,525,403 10/1950 De Witt ..72/309 3,511,074 5/l970 Grees ..72/389 Primary Examiner-Charles W. Lanham Assistant Examiner-Michael J. Keenan Attorney-Jean L. Carpenter and Arthur N. Krein ABSTRACT A tube bending apparatus for simultaneously forming multiple bends in metallic tubing, the tubing being secured at opposite ends and a plurality of double actuating forming or bending heads being used to form the bends, one such double actuating bending head being used for each of the bends.

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A TTOPNEY PATENTEDMAY 16 I972 SHEET 0F 4 A T TOPNEY TUBE BENDER This invention relates to a tube bender and, in particular, to a tube bending apparatus capable of simultaneously forming multiple bends in a metallic tube.

Heretofore, the prevalent method of making multiple bends in tubing was performed by making the bends sequentially, usually beginning with a bend near the center of the tube, with the remaining bends then formed progressively toward the ends of the tube. These bends were performed by a variety of bending techniques usually involving sliding shoes and dies or wrapping mechanisms which carefully supported the tube to assure tight bends and prevent crushing of the tube. For a complicated series of bends, a fixture was generally designed and assembled by skilled builders using trial and error methods. These fixtures usually required weeks to assemble and try out and presented many difficult problems in their setup and adjustment, primarily due to variations in tube stiffness since each bend is affected by any subsequent bends. In addition, these prior art fixtures were usually scrapped when a new part design was substituted.

This prior art method of forming bends in a tube was rather costly and time consuming, especially when one considers that in the automotive field, steel brake and gas lines used in a vehicle may be as long as 12 feet and have 30 or more bends formed therein.

It is therefore a primary object of this invention to provide a tube bender adapted to the simultaneous formation of multiple bends in metallic tubing.

Another object of this invention is to provide a tube bending apparatus, adapted to use a plurality of tube bending heads, each bending head being adapted to be simultaneously actuated with the remaining bending heads whereby the bend formed by each such head is made simultaneously but completely independent of the bends formed by the other tube bending heads of the apparatus.

Still another object of this invention is to provide a tube bending apparatus of simplified construction to effect the simultaneous formation of multiple bends in metallic tubing.

These and other objects of the invention are obtained by means of a tube bending apparatus utilizing a plurality of double actuating tube bending heads for simultaneously forming multiple bends in metallic tubing whereby a straight piece of tubing to be bent is brought into contact with all of the forming heads at one time when the machine is loaded, the tube being held rigidly at opposite ends by suitable clamps, after which all of the forming heads are powered simultaneously to rotate in the plane-of-bend in which they were set up relative to one another and thereby carry the tube with them to its final form position.

For a better understanding of the invention, as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a view of a portion of a tube bending apparatus employing a plurality of double actuating forming heads to make a plurality of bends in a tube;

FIG. 2 is a view taken along line 22 of FIG. 1 with parts broken away to show the details of the hydraulic power actuator portion of one of the forming heads;

FIG. 3 is a top view of one of the forming heads of the tube bending apparatus of FIG. I;

F IG. 4 is a view taken along line 4-4 of FIG. 3;

FIG. 5 is a perspective view of one of the double actuating forming heads of the tube bending apparatus illustrating how the bending actuator can be mounted in different positions relative to the interconnecting pads;

FIGS. 6 and 6a are schematic perspective views of a single forming head to show the relative position of the interconnecting pads of the forming head in forming a single tube bend; and,

FIG. 7 is a schematic perspective view of a pair of forming heads interconnected to each other to form a pair of tube bends.

Referring now to FIG. 1, there is shown a portion of a tube bending apparatus constructed in accordance with the invention and having a plurality of forming heads connected together and shown in position relative to each other after a tube bending operation. Although only three forming heads are shown, it is to be realized that any number of forming heads can be utilized to effect the final desired configuration of the tube.

As shown somewhat schematically in FIG. I, a tube 10, originally straight in configuration, is secured at opposite ends in suitable tube clamps 12, only one of which is shown, and intermediate its fixed ends it is gripped by a plurality of forming heads 20, only three of which are shown, suitably positioned annularly and in the desired plane with respect to each other so that upon relative rotation of the forming heads with respect to each other and from their original fixed plane position, the original straight tube 10 is now bent to the configuration shown, as described in detail hereinafter.

The bending apparatus of the invention provides an apparatus for bending a tube wherein the straight piece of tube to be formed is positioned in contact with all of the forming heads and fixed at opposite ends by tube clamp 12 when the tube is loaded in the apparatus; wherein, while the tube is being held rigidly at opposite ends between the tube clamps, all of the forming heads are powered as described hereinafter, to rotate in a preplanned plane of bend in which they are set up relative to each other to carry the tube with them to its final form configuration.

Referring now to FIGS. 2 through 5, inclusive, there is shown one of the forming heads, generally designated 20, of the tube bending apparatus. Each of the forming heads 20 is provided with a pair of mounting pads 22 and 24 whereby the forming heads can be interconnected to the next adjoining head or to a fixed support as described hereinafter. The forming head is constructed so that the pads 22 and 24 of a forming head can be rotated relative to each other by a bending actuator, such as by a hydraulic actuator or motor 26 through a rack and pinion arrangement described hereinafter. The number of degrees of bend or relative rotation of pad 22 with respect to pad 24 is controlled by adjustable stop screws 28 and 28a, as described, which limit the travel of the rack of the rack and pinion arrangement and therefore the relative rotation of pad 22 with respect to pad 24. Each forming head is provided with a tube engaging mandrel or jaw 30 that is arranged on the forming head for movement from a first position in which it will grip the tube to be bent to a second or collapsed position, shown in dotted line in FIG. 4,'to release the tube after forming to permit the then formed tube to drop out of the forming heads. The tube engaging jaw 30 is collapsed by means of a collapsible head operator, such as an air cylinder or motor 32 secured to the rear of the forming unit, and operating on the tube engaging jaw in a manner to be described in detail hereinafter.

The mounting pads 22 and 24 on the forming head are used to interconnect the forming heads together in any desired configuration to effect forming of the desired bends in a tube. Thus, for example, with reference to FIG. 1, the pad 22 of the first forming head is connected to the fixed bracket 1 I carrying the tube clamp 12 while its pad 24 is connected by a support bracket 13 to the pad 24 of the second forming head, the second forming head having its pad 22 connected to pad 22 of the third forming head by bracket 14. This sequence of connecting end pads 22 or 24 of one forming head to either of pads 22 or 24 of the next forming head is continued for all of the forming heads of the tube bender, the last forming head again being connected by either pad 22 or pad 24 thereon to the fixed support carrying the tube clamp 12 at the opposite end of the unit.

In the preferred embodiment of the forming heads illustrated, each forming head 20 includes a power actuator housing 40 connected at right angles to a head housing 41 by bolts 46 to form a casing housing the rack and pinion arrangement used to effect relative rotation between pads 22 and 24 of each forming head. As shown in FIG. 2, the actuator housing 40, having the pad 24 formed at one end thereof, is provided with a through bore 42 to slideably receive the gear rack 43 for reciprocating movement therein, the through bore being threaded at one end to receive the adjusting stop screw 28 which can be adjustably positioned therein to limit travel of the gear rack in one direction, to the right as seen in FIG. 2, the position of the adjusting screw being maintained by means of a set screw 44. The gear rack 43, which can be formed as a separate element connected to the piston rod or, as shown, the gear rack 43 can be formed integral with one end of the piston rod 45 of the hydraulic motor 26 which is secured, as by bolts 46, to the actuator housing 40. The opposite end of the hydraulic motor is provided with a threaded cylinder head 47 having a threaded lock plate 48 secured thereto to receive the adjusting screw 280, which through contact with the piston rod limits movement of the gear rack 43 in the opposite direction, to the left as seen in FIG. 2.

The hydraulic motor 26 is a conventional double acting reciprocating piston-type motor, and as such need not be described in detail since its construction forms no part of the subject invention. The hydraulic motor 26 is connected by flexible hoses 51 and 52 to a suitable source of hydraulic fluid under pressure, the flow of which is controlled by suitable control valves, not shown, to effect reciprocation of the piston rod 45 and gear rack 43, in the direction desired. All of the hydraulic motors 26 of the forming heads are connected through the control valves to a common manifold, not shown, so that all of these hydraulic motors are simultaneously operable to efl'ect simultaneous bending of a tube.

The actuator housing 40 is also provided with a cross-bore 53 for the pinion gear 54 which is positioned to be in engagement with the gear rack 43 and is connected by keys 55 to a hollow shaft 56 suitably journaled in the housing 41. At its left end, as seen in FIG. 4, shaft 56 is also connected by the keys 55 to an annular motor support flange 57 and secured thereto, as by an end nut 58 threaded onto the left end of the shaft. The end nut 58 is threaded onto the shaft 56 to position the support flange 57 against one side of the pinion gear 54 whereby it is held in axial alignment on the shaft 56 by this flange'57 abutting against one side of it and on the opposite side by a thrust ring 59 encircling the shaft between it and the left-hand end of the housing 41, as seen in this figure. With this arrangement, the support flange 57, and the air motor 32, which is secured thereto as by bolts 61, are adapted to rotate with the shaft 56.

As shown in FIG. 4, the shaft 56 extends through the housing 41 and is provided at its right-hand end, as seen in this figure, with flat portions 62 thereon and a threaded end 63, the thus squared end of the shaft formed by these flat portions being engaged in a complementary shaped bored portion 64 of a pad casing 65 on which the pad 22 is formed. The pad casing 65 is retained in driven position on the shaft 56 by means of a nut 66 engaging the threaded end portion 63 of the shaft 56, a thrust washer 67 encircling the shaft 56 between the housing 41 and the pad casing 65. With this arrangement, as shaft 56 is rotated within the housing 41, the pad casing and therefore the pad 22 is rotated relative to the pad 24 on housing 41.

A counterbored guide block 68 is secured, as by bolts 71, to the end of pad casing 65, with the bore therein concentric to the axis of bore 64 on the pad casing, to pivotally support the tube engaging jaw 30.

As shown in FIGS. 3 and 4, the tube engaging mandrel or jaw 30 is pivotally connected to a mandrel or jaw guide portion 73 of the guide block 68 by a pivot pin 74 extending through suitable apertures in the bifurcated leg ends 75 of the tube engaging jaw 30 and in the guide portion 73, the pivot pin being held in place by a lock plate 76 secured to one leg end 75 of tube engaging jaw 30 with the lock plate 76 engaged in a suitable lock notch formed in the pivot pin 74.

In addition, the bifurcated leg ends 75 of the tube engaging jaw 30 are provided with arcuate slots 77 and the guide portion 73 of the guide block 68 is provided with a straight slot 78 to receive an actuator pin 81 to eflect oscillation of the tube engaging jaw between a tube gripping position as seen in solid line in FIG. 4 to a tube release position shown by the broken lines in this same figure. The actuator pin 81 is secured by a set screw 82 in the jaw actuator 83 threaded to one end of the piston rod 84 of the air motor 32, the piston rod extending from the air motor through the hollow shaft 56 into the guide block 68, with the jaw actuator 83 thereon being slidably journaled in the guide block and in a portion of the tube engaging jaw 30.

The forward or free end of the tube engaging jaw 30 is provided with a tube receiving notch 85 of a suitable width to receive the tube. In addition, the tube engaging portion of the tube jaw is shaped with a radius complementary to the desired radius of curvature of the tube bend effected by this tube engaging jaw 30.

The air motor 32 is a conventional double acting reciprocating piston-type pneumatic motor, and as such, need not be described in detail since the details of its construction form no part of the subject invention. Air motor 32 is connected by flexible hoses 86 and 87 to a suitable source of pneumatic fluid under pressure with the flow to and from opposite ends of the air motor being controlled by suitable control valves, not shown, to effect reciprocation of the piston rod 84 and jaw actuator 83, as desired. All of the air motors 32 for the forming heads are connected by these valves to a common manifold, not shown, so that operation of the air motors can be effected simultaneously whereby the tube is simultaneously gripped or released by the tube engaging jaws.

Referring now to FIG. 5, the flanges 88 of the actuator housing 40 in the embodiment shown, are provided with equally spaced threaded holes to receive the bolts 46 securing the head housing 41 to the actuator housing. This permits different angular assembly arrangements of the mounting pads 22 and 24 relative to each other and to permit assembly of rightand left-hand units, a right-hand unit being shown in FIG. 5, to facilitate setting up the various forming heads relative to each other in order to obtain the desired tube bends. Thus, for example, in FIG. 5, the mounting pad 22 is originally positioned at right angles relative to the mounting pad 24, while in FIG. 4 these mounting pads are positioned relative to each other, both being right-hand units, that is, the hydraulic motor 26 being mounted on the right-hand side when viewed from the jaw end of the forming head.

Referring now to the operation of the forming heads, there is shown schematically in FIGS. 6 and 6a the procedural steps for forming a single bend in a tube 10. As shown in FIG. 6, a tube 10 is held rigidly by clamps 12a and 12b from mounting pads 22 and 24, respectively, with the tube in contact with a tube engaging jaw 30 of the single forming head 20. Upon actuation of the hydraulic motor, not shown in these figures, the mounting pads 22 and 24 are moved relative to each other to the position shown in FIG. 6a to form a single bend in the tube 10.

Similarly, if a series of forming heads are connected together and all of them are actuated simultaneously to rotate relative to one another, a series of bends will be formed. Thus, for example, there is shown in FIG. 7 a pair of forming heads 20 interconnected together to form two bends in the tube 10. As shown schematically in FIG. 7, to efiect the bending of the tube to the position shown therein, the mounting pad 22 of one of the forming heads 20, the left-hand forming head shown in this figure, is rigidly secured by a bracket 13a to the pad 24 of a second forming head, right-hand forming head shown in this figure. The tube 10 is held rigidly at opposite ends by tube clamps 12a and 12b secured to the mounting pads 24 and 22 of the left-hand and right-hand forming head, respectively, as seen in this figure. Upon actuation of the hydraulic motors 26, not shown in this figure, of these forming heads, relative rotation of the pads 22 and 24 of each of the forming heads is effected in the direction of the arrows to the position shown in this figure to simultaneously form the tube bends shown. As can be seen in FIG. 7 and from the above description, it is apparent that either mounting pad 22 can be rotated relative to the mounting pad 24 which is fixed against rotation, as in the right-hand forming head of FIG. 7, or alternately, mounting pad 22 can be fixed against rotation and mounting pad 24 moves relative thereto as in the left-hand forming head of FIG. 7. When the latter occurs, it is obvious that the entire assembly fixed to the head housing 41 with the mounting pad 24 thereon is moved, including the hydraulic motor 26 of this unit.

It is also apparent from F IG. 7 that the pads 22 and 24 can either be rotated clockwise or counterclockwise relative to each other and this can be accomplished on either the righthand or the left-hand units by controlling the flow of pressurized hydraulic fluid to the hydraulic motors 26 to efiect movement of the piston rod in the proper direction to attain the desired rotation of these pads relative to each other.

Referring again to FIG. 1, in the embodiment shown, the tube clamp 12 is supported by a support bracket 11 which is also connected to mounting pad 22 of the lowermost forming head 20. The lowermost forming head 20 is then connected to the intermediate forming head 20 by a bracket 13 connected at opposite ends to the mounting pads 24 of these forming heads. In turn the intennediate forming head 20 is connected to the uppermost forming head 20 by a bracket 14 connected at opposite ends to the mounting pads 22 of these forming heads. The uppermost forming head 20, shown in FIG. 1, would then be connected to the next forming head, not shown, by bracket 15 with each additional forming head being connected in a similar manner to complete the assembly of the tube bender. The last forming head in this assembly would then be connected to the tube clamp 12, not shown, which would grip the opposite end of the tube 10.

Desirably, one of the brackets, for example, bracket 11 in FIG. 1, is fixed relative to the ground and the remaining elements of the tube bender apparatus can then be suspended from an overhead beam, not shown, as by flexible mountings, such as flexible cable 16 secured to bracket 13, which support the component weight of the tube bender elements, but allow the forming heads to assume the appropriate positions to form the tube bends as the bends of these forming heads articulate.

This mounting arrangement permits the forming heads 20 to be positioned with their tube engaging jaws at the proper distance from each other along the tube and permits proper relative radial placement of the forming heads, which position is dictated by the plane in which the bends in the tubing will be made as determined by the X, Y and Z coordinates used to define the finished tube shape. As is well known in the tube bending art, the X, Y and Z coordinates are measured from one end of the tube to the center of a bend along the center line of the tube.

The tube clamps 12 may be manually operable or, as shown in FIG. I, may each be operated by means of a pneumatic motor 18 having the clamp 12 fixed to the piston rod 17 thereof whereby to effect movement of the tube clamp 12 relative to the bracket 11 between a tube clamping position and a tube release position. The pneumatic motor 18 is preferably similar in construction to the air motors 32 and is connected by suitable air hoses 19, only one being shown, at opposite ends of this motor, the hoses being connected by suitable control valves, not shown, to a source of pressurized pneumatic fluid so that the air motors for the two clamps are operated simultaneously.

In the operation of the tube bending apparatus of the invention, the forming heads are positioned through actuation of the hydraulic motors 26 to position the forming heads into the tube loading position and the air motors 32 are actuated to place the tube engaging jaws in a tube release position as shown in broken lines in FIG. 4. A section of straight tube 10 is then loaded into the tube clamps 12 and then the pneumatic motors 18 are actuated to move the tube clamps into the tube clamping position, as previously described. The air motors 32 are then energized to move the tube engaging jaws into engagement with the tube.

After this the hydraulic motors 26 are then actuated to effect simultaneous rotation of the mounting pads 22 and 24 of the forming heads relative to each other to effect bending of the tube 10 to the desired configuration. After bending of the tube is completed, the air motors 32 are actuated to move the tube engaging jaws to the position shown by broken lines in FIG. 4 to release the tube 10 and the air motors 18 are actuated to move the tube clamps 12 to a tube release position thus allowing the now bent tube 10 to fall from the tube bending apparatus. After this, the hydraulic motors are again actuated to rotate the mounting pads 22 and 24 of the forming heads relative to each other to bring these mounting pads back to their original position and ready for another tube bending operation. The tube bending apparatus is now in condition to accept a straight section of tube 10 in preparation for another bending cycle.

What is claimed is:

1. In a tube bending apparatus for simultaneously forming multiple bends in a tube, the combination including a pair of clamp means positioned to grip opposite ends of a straight tube to be bent, an N number of forming heads, each of said forming heads including a pair of easing means each having a mounting pad thereon rotatively mounted with respect to each other and, a tube engaging means connected to one of said casing means, power actuator means operatively connected to one of said casing means to efiect rotation of said casing means and therefore said pads with respect to each other; and N+l number of mounting means for interconnecting said forming heads together by said mounting pads and to operatively connect said forming heads to said clamp means with said tube engaging jaw means of said forming heads positioned to engage the tube between said clamp means whereby, as said pads are rotated with respect to each other, said tube engaging means of said forming heads are moved relative to each other and to said clamp means to effect bending of the tube.

2. In a tube bending apparatus according to claim 1 wherein each of said clamp means includes a tube clamp and a fluid pressure operated motor connected to one of said mounting means and to said tube clamp to effect movement of said tube clamp between a tube engaging position and a tube release position relative to said one of said mounting means.

3. In a tube bending apparatus according to claim 1 wherein said tube engaging means includes a tube engaging jaw, a tube jaw guide portion operatively connected to one of said casing means of a forming head for movement therewith, said tube engaging jaw being pivotally supported by said tube jaw guide portion for movement between a tube engaging position and a tube release position and, power means operatively connected to said tube engaging jaw to effect movement of said tube engaging jaw between said tube engaging position and said tube release position.

4. In a tube bending apparatus according to claim 3 wherein said power actuator means is a fluid pressure operated motor means fixed to one of said casing means and operatively connected to the other of said casing means having said tube jaw guide portions connected thereto.

5. In a tube bending apparatus according to claim 1 wherein said power actuator means includes a reciprocating fluid pressure operated motor connected to one of said casings, said reciprocating fluid pressure operated motor having a piston rod with a gear rack operatively connected thereto, a pinion gear positioned in engagement with said gear rack and operatively connected to said other one of said casing means to effect rotation of said pair of said casing means of said forming head relative to each other, and adjustable means connected to said reciprocating fluid pressure operated motor to control the length of stroke of said piston rod.

6. In a tube bending apparatus for simultaneously forming multiple bends in a tube, the combination including a first clamp means, a second clamp means, an N number of forming heads, each of said forming heads including a first casing means with a mounting pad thereon and second casing means with a mounting pad thereon, drive means rotatively connecting said first casing means to said second casing means, power actuator means connected to said first casing means and to said drive means to effect rotation of said second casing means relative to said first casing means, said second casing means including a mandrel support portion, a tube bending mandrel mounted on said mandrel support portion for movement between a tube engaging position and a tube release position, power means operatively connected to said mandrel to effect movement of said mandrel between said tube engaging position and said tube release position and, N+l number of 10 mounting means connecting said first clamp means, said forming heads, and said second clamp means together in series with said first clamp means positioned to engage one end of the tube, said second clamp means positioned to engage the opposite end of the tube and with said forming heads positioned whereby said mandrels are adapted to engage the tube between said first clamp means and said second clamp means, said mounting means being connected to said mounting pads of said first casing means and said second casing means of said fonning heads whereby said forming heads can be articulated with respect to each other.

7. in a tube bending apparatus according to claim 6 wherein said first clamp means and said second clamp means, each including a tube clamp and power means connected to said tube clamp to effect movement of said tube clamp between a tube engaging position and a tube release position.

8. A tube bending apparatus according to claim 6 wherein said power actuator means is a fluid pressure operated reciprocating motor having a piston rod with a gear rack operatively connected thereto, a pinion gear connected to said drive means and positioned for engagement with said gear rack.

9. In a tube bending apparatus according to claim 6 wherein said drive means to effect rotation of said second casing means relative to said first casing means is a hollow shaft journaled for rotation in said first casing means and fixed at one end to said second casing means, said power means operatively connected to said mandrel including a fluid pressure operated motor having a piston road extending through said hollow shaft and operatively connected at one end to said mandrel to effect movement of said mandrel between said tube engaging position and said tube release position. 

1. In a tube bending apparatus for simultaneously forming multiple bends in a tube, the combination including a pair of clamp means positioned to grip opposite ends of a straight tube to be bent, an N number of forming heads, each of said forming heads including a pair of casing means each having a mounting pad thereon rotatively mounted with respect to each other and, a tube engaging means connected to one of said casing means, power actuator means operatively connected to one of said casing means to effect rotation of said casing means and therefore said pads with respect to each other; and N+1 number of mounting means for interconnecting said forming heads together by said mounting pads and to operatively connect said forming heads to said clamp means with said tube engaging jaw means of said forming heads positioned to engage the tube between said clamp means whereby, as said pads are rotated with respect to each other, said tube engaging means of said forming heads are moved relative to each other and to said clamp means to effect bending of the tube.
 2. In a tube bendiNg apparatus according to claim 1 wherein each of said clamp means includes a tube clamp and a fluid pressure operated motor connected to one of said mounting means and to said tube clamp to effect movement of said tube clamp between a tube engaging position and a tube release position relative to said one of said mounting means.
 3. In a tube bending apparatus according to claim 1 wherein said tube engaging means includes a tube engaging jaw, a tube jaw guide portion operatively connected to one of said casing means of a forming head for movement therewith, said tube engaging jaw being pivotally supported by said tube jaw guide portion for movement between a tube engaging position and a tube release position and, power means operatively connected to said tube engaging jaw to effect movement of said tube engaging jaw between said tube engaging position and said tube release position.
 4. In a tube bending apparatus according to claim 3 wherein said power actuator means is a fluid pressure operated motor means fixed to one of said casing means and operatively connected to the other of said casing means having said tube jaw guide portions connected thereto.
 5. In a tube bending apparatus according to claim 1 wherein said power actuator means includes a reciprocating fluid pressure operated motor connected to one of said casings, said reciprocating fluid pressure operated motor having a piston rod with a gear rack operatively connected thereto, a pinion gear positioned in engagement with said gear rack and operatively connected to said other one of said casing means to effect rotation of said pair of said casing means of said forming head relative to each other, and adjustable means connected to said reciprocating fluid pressure operated motor to control the length of stroke of said piston rod.
 6. In a tube bending apparatus for simultaneously forming multiple bends in a tube, the combination including a first clamp means, a second clamp means, an N number of forming heads, each of said forming heads including a first casing means with a mounting pad thereon and second casing means with a mounting pad thereon, drive means rotatively connecting said first casing means to said second casing means, power actuator means connected to said first casing means and to said drive means to effect rotation of said second casing means relative to said first casing means, said second casing means including a mandrel support portion, a tube bending mandrel mounted on said mandrel support portion for movement between a tube engaging position and a tube release position, power means operatively connected to said mandrel to effect movement of said mandrel between said tube engaging position and said tube release position and, N+1 number of mounting means connecting said first clamp means, said forming heads, and said second clamp means together in series with said first clamp means positioned to engage one end of the tube, said second clamp means positioned to engage the opposite end of the tube and with said forming heads positioned whereby said mandrels are adapted to engage the tube between said first clamp means and said second clamp means, said mounting means being connected to said mounting pads of said first casing means and said second casing means of said forming heads whereby said forming heads can be articulated with respect to each other.
 7. In a tube bending apparatus according to claim 6 wherein said first clamp means and said second clamp means, each including a tube clamp and power means connected to said tube clamp to effect movement of said tube clamp between a tube engaging position and a tube release position.
 8. A tube bending apparatus according to claim 6 wherein said power actuator means is a fluid pressure operated reciprocating motor having a piston rod with a gear rack operatively connected thereto, a pinion gear connected to said drive means and positioned for engagement with said gear rack.
 9. In a tube bending apparatus according to cLaim 6 wherein said drive means to effect rotation of said second casing means relative to said first casing means is a hollow shaft journaled for rotation in said first casing means and fixed at one end to said second casing means, said power means operatively connected to said mandrel including a fluid pressure operated motor having a piston road extending through said hollow shaft and operatively connected at one end to said mandrel to effect movement of said mandrel between said tube engaging position and said tube release position. 